The present invention relates to an apparatus for germ reduction of a fluid. The present invention also relates to a process for using said apparatus for reducing the germ count of a fluid containing germs and the use of said apparatus for germ reduction of fuel oil, of food products, or water decontamination, preferably decontamination of waste water, industrial process water, or the treatment of drinking water.
Germ reduction of fluids is of widespread commercial interest, for example, for sanitation, hygiene and drinking water purposes and in the medical and food industries. The term “germ” in the present application is not specifically limited and it is defined as a microorganism, particularly pathogenic or spoilage ones.
Various types of apparatuses for germ reduction of fluids are known, and they are generally based on filtering apparatuses. For example, WO 2004/052961 A1 discloses a variety of such filtering apparatuses making use of special guanidine copolymers as the germ-reducing material. These copolymers, however are disclosed in the form of either water soluble or gel materials only. It is noted that water soluble or gel materials are not stable materials for construction of devices and their components. Water soluble or gel materials generally also do not have long-term stability when exposed to fluids, and, for example, they may deform or lose their active components. It is generally undesirable for the potentially toxic water-soluble biocide materials of the prior art to leach out of the apparatus and its components due environmental, health and safety and (other) regulatory aspects.
In the disclosed filtering apparatuses the guanidine copolymer is in the form of a granulate, powder or gel and packed into a filtration column through which the fluid to be treated is then passed. Alternatively it is disclosed that the guanidine copolymer may be coated onto a paper, cellulose or fabric material, which is then used as a filtering element in the apparatus. Filtration devices suffer from the disadvantage that their use entails significant pressure drops. These pressure drops result from their limited void fraction and high specific surface—both of which are used to achieve a high interfacial contact between the fluid and the solid phase.
Although guanidine based polymers are effective in germ reduction, they—like most germ-reduction materials—are not yet a commodity material, and thus they are still relatively expensive specialty polymers only available in limited production volumes from specialty polymer producers. The relatively high cost of such germ-reducing materials (biocides) then results in a drawback of such known filtering apparatuses for germ reduction. Such filtering devices generally require the use of relatively large quantities of expensive germ-reducing material. This is because filter columns typically have only relatively small void fractions for contact of the fluid to be treated with the biocide, and thus they require longer columns or lower flow rates for a particular specific surface area in order to generate sufficient residence time to be effective. Furthermore limitations to the usable specific surface area arise due to pressure drop considerations.
In addition, in the case of filtering apparatuses making use of columns of biocide in the form of granulate, powder or gel, as in WO 2004/052961, a very large fraction of the biocide is “wasted”, as only the outer surface of the granulate, powder or gel contacts the fluid and is effective. The bulk of the biocide in the interior of the granulate, powder or gel is thus inactive due to a lack of contact with the fluid.
In conclusion, it would be desirable to have an apparatus for germ reduction of a fluid which makes more efficient use of expensive specialty biocide materials. Such an apparatus would allow for a more efficient germ reduction for a given quantity of biocide. It would furthermore be desirable if said apparatus did not suffer from the disadvantages of high pressure drops or lack of long-term stability upon exposure to fluids, such as due to leaching out of the biocide. Furthermore it would be preferred if the germ reduction could be improved even still further relative to that of the state of the art filtering apparatuses.